HIV/AIDS is increasingly a disease of the disadvantaged; care is moving out of the major epicenters and treatment centers into dispersed communities and practice settings. Policymakers, health care providers, and HIV patients need accurate information that is relevant to these trends on the delivery of care, sources of financing, and patient outcomes. Unbiased estimates at the national level, necessary for statistical inferences to the population of interest, currently are lacking. Therefore, we propose to cooperate with AHCPR in collecting data on a national probability sample of persons with HIV/AIDS and their providers. The study will enroll 4000 randomly-selected subjects receiving care in 18 states and the District of Columbia from about 60 major and 120 smaller providers in 30 randomly-selected locales and from 3 purposefully-selected supplemental rural sites. Data collection will consist of a baseline interview, follow-up interviews at 6, 12 and 18 months, and medical (on 1 or 2 occasions) and billing record abstraction for data on utilization, costs and severity. The research team includes: investigators from RAND, NORC, Project HOPE, Harvard Brown, Miami and Boston Universities, Jefferson, Mt. Sinai and Charles Drew Medical Colleges, UCLA, UCSD, San Francisco Department of Public Health, Kaiser-Permanente of Northern California, and other institutions, as well as leading HIV/AIDS providers in the communities sampled who will facilitate execution of the study and participate in scholarly work. Members of the HIV community will have a strong role in the project. To facilitate cooperation with AHCPR, all major meetings of the study team, and meetings of the community and scientific advisory panels, will be held in Washington. This project will examine use and costs of medical and nonmedical services and how they vary geographically, across health care systems and patient clinical and demographic characteristics; examine variations in access to care, unmet needs for services, health-related quality of life, social support, quality of care, clinical epidemiology, satisfaction with care and knowledge about HIV/AIDS; validate measures of severity and staging; evaluate transitions in principal provider of care, and conduct special studies on HIV infection among women (to be sampled at twice the rate of men) and children (n=400), in rural areas (n=400), on mental health and dental care, and on formal and informal caregivers. We will estimate lifetimes costs of HIV treatment and the impact of health reform and therapeutic advances, as well as analyze ACSUS data to provide continuity with previous work. These data will provide national estimates of the impact of HIV that can answer a broad range of questions and will allow analyses of how care varies across sites, including those at the frontiers of the epidemic. The data will be made available for public use, and the project's investigators will respond rapidly to policy-related requests for data and additional studies.